1. Field of the Invention
This invention relates to additives which improve the compressive strength and workability of cementitious compositions such as cement, cement slurries, mortar, grout and concrete.
2. Description of the Prior Art
Concrete is a hard, strong building material made by mixing cement, sand, gravel and water. Water in the mixture causes the cement to set and bind the entire mixture in a hard mass. It is well known in concrete technology that the strength--usually the compressive strength as measured by the ASTM test C39-72--is a reliable criterion of general quality. For this reason, the whole technology of concrete is developed around obtaining a significant and practical strength with a minimum of cost, and a maximum of convenience in use. Despite extensive research, most of the concrete presently being used are simple mixtures of sand and coarse stone containing a minor proportion of portland cement with sufficient water being added to produce a mixture fluid enough to place in forms.
It is well known in the art that reducing water in concrete increases the compressive strength and other properties as well. Considerable research has been directed to discovering mixtures of different particle sizes of sand and stone which will give fluid concrete having minimum water content. Also, various organic and inorganic additives have been found which permit reduction in the water content of concrete. One such additive, the sodium salt of naphthalene sulfonic acid formaldehyde condensate is used commercially for this purpose. This additive also increases the strength of hardened concrete. See U.S. Pat. No. 2,141,569--Tucker--Dec. 27, 1938.
Further, U.S. Pat. No. 3,537,869--Proell--Nov. 3, 1970 describes use of additives containing sulfonated condensation products of formaldehyde and naphthalene or salts thereof in combination with lecithin, partial fatty acid esters of polyols, their ethoxylates, sulfates, etc., in concrete mixes to increase compressive strength of the hardened concrete.
Additionally, use of resorcinol-formaldehyde and catechol-formaldehyde resin in cement and concrete is shown below.
U.S. Pat. No. 3,216,966--Collins et al--Nov. 9, 1965 describes an ultra high strength concrete composition containing an in situ cross-linked condensation product of resorcinol or phloroglucinol and formaldehyde or glyoxal.
CA 75 51101q describes an oil well plugging mixture composed of portland cement and 15% phenolic resin, e.g., resorcinol-formaldehyde resin, hardened with formalin or paraformaldehyde.